This is the second in a series in five parts at Breitbart.com based on the new book, "American Betrayal: The Secret Assault on Our Nation’s Character" (St. Martin’s Press) by Diana West.Pt. 1 is here.

It’s difficult to imagine someone more important in U.S. history than Harry Hopkins, but Americans don’t learn much more than his name, if that, in school.

This means we aren’t taught that Hopkins, FDR’s top wartime advisor, ran what became known as “Roosevelt’s own personal Foreign Office” from the Lincoln Bedroom, where Hopkins lived for three-and-half-years. We aren’t taught that this former social worker in key ways controlled U.S. foreign policy by controlling the distribution of U.S. military materiel to countries at war through his supervision of the massive Lend Lease program. We aren’t taught he attended the famous wartime conferences as de facto “foreign minister.” We certainly aren’t taught that Lend Lease, perhaps even Hopkins himself, pushed uranium and other A-bomb essentials through to Stalin.

These uranium shipments, erased from our historical memory but documented by Congress in 1950, took place at a time when the atomic development program known as the Manhattan Project was, we thought, our most precious secret.

Why would Lend Lease, overseen by Hopkins -- who was also, not incidentally, FDR’s liaison to atomic research -- do such a thing?

The answer may relate to something else we don’t learn about Harry Hopkins: FDR’s powerful wartime advisor may have been a Soviet agent -- and “the most important of all Soviet wartime agents.”

This was the estimation of Iskhak Ahkmerov, the famed Soviet “illegal” who ran a stable of top spies for the Kremlin, including Alger Hiss. Oleg Gordievsky, a former KGB colonel and trusted defector, reported in his 1990 book KGB, co-authored with Christopher Andrew, that he heard Akhmerov single out Hopkins as the Soviets’ No. 1 agent in a lecture to KGB officers in the 1960s.

In 1957, George Marshall, the former Secretary of State who earlier served alongside Hopkins as FDR’s Army Chief of Staff, made a curiously complimentary statement to his official biographer: “Hopkins’s job with the president was to represent the Russian interests. My job was to represent the American interests.”

Meanwhile, Hopkins himself is quoted in the New Yorker as saying: “I had the Russian story for the president... The political implications of extending Lend Lease to Russia” -- a dictatorship, which by the time of the wartime alliance had already killed more people than Hitler ever would -- “never bothered me.”

Was Harry Hopkins really no more than “an articulate propagandist for all-out aid to Russia?” Or does the record reveal actions more befitting of a “most important Soviet agent?”

American Betrayal devotes much more space than is available here to lay out a case for the latter, but consider one example from the once-secret Soviet record.

In May 1943, Hopkins received a confidential letter from FBI Director J. Edgar Hoover addressed to both Hopkins and the president. The letter revealed Soviet plans to infiltrate “industries engaged in secret war production for the United States Government so that information could be obtained for transmittal to the Soviet Union.” This information came from a wiretapped conversation between a Soviet Comintern agent -- masquerading, Hoover explained, as a top diplomat at the Soviet embassy -- and a known American Communist underground operative. Later, the FBI would realize this tapped conversation was its first inkling of the massive Soviet atomic espionage ring.

What did Hopkins do with this highly sensitive information? Did he share, let alone discuss it with FDR? We don’t know. We do know from the Mitrokhin archive, thousands of KGB documents copied by former KGB archivist Vasili Mitrokhin, that Hopkins “privately warned” the Soviet embassy that their agents were under FBI surveillance!

Hopkins’ decisive action would seem to debunk claims that he was “naïve” in his Soviet partisanship, but the consensus on Hopkins among students of intelligence history remains unsettled.

There’s more evidence to consider, however. For example, after the war, Congressional hearings established the fact that FDR’s Lend Lease program sent the U.S.SR uranium, heavy water, and other atomic program essentials (including $13 million worth of aluminum tubes, which are necessary to “cook” uranium into plutonium). When the Manhattan Project’s Gen. Leslie Groves embargoed U.S. uranium stocks to prevent more such shipments, Lend Lease, it is also documented, circumvented the embargo by tapping Canadian stocks of uranium.

We have an American witness to this treachery. After Stalin stunned the world by exploding an atomic bomb in 1949 -- a development, Soviet intelligence archives show, that emboldened him to trigger the Korean War at a cost of millions of lives -- a whistleblower came forward to call attention to the wartime atomic shipments to Moscow. His name was George Racey Jordan, and he had served as the top U.S. Lend Lease “expediter” at the supply hub in Great Falls, Montana.

One day, Jordan said he was called to the phone to talk to a man about a shipment of chemicals that needed expediting.

“I don’t want you to discuss it with anyone,” the man on the phone said, “and it is not to go on the records. Don’t make a big production of it, but just send it through quietly, in a hurry.”